Method and apparatus for coating films



March 10, 1970 H. P. FRY, JR

METHOD AND APPARATUS FOR COATING FILMS Filed Feb. 17, 1967 United StatesPatent US. Cl. 117-111 8 Claims ABSTRACT OF THE DISCLOSURE A method andapparatus is disclosed in which a layer of coating material ofcontrolled thickness is applied to a film having longitudinal elementsof different length by a transfer roller which is contoured to cause thefilm to contact therewith generally evenly across its entire width.

The present invention relates to an improved method and apparatus forcoating continuous films.

During the manufacture of regenerated cellulose films, as well as filmsformed of other materials, forces within and/or applied to the filmoften cause the longitudinal edge portions of the film to be longer thanother portions and particularly the mid-portions thereof. The longeredge portions of such film, referred to in the art as floppy edges,present a wavy edge outline which makes subsequent film processing, andparticularly coating, diflicult to control.

Generally, coating of such film is performed by a kiss coating processin which a thin layer of coating material is deposited onto the surfaceof a roating cylinder and then transferred to a surface of the film asit is advanced relative to and temporarily in contact with the transfercylinder. Since the film being coated has longitudinal edge elementswhich differ in length from the remainder of the film, uniform contactof the film with the rotating cylinder, across the entire film width,cannot be achieved and results in poor coating transfer. Accordingly, aprimary object of this invention is to provide a generally new orimproved and more satisfactory method and apparatus for coatingcontinuous films.

Another object of this invention is to provide an improved method andapparatus for applying a layer of coating material of controlledthickness onto a traveling continuous film having longitudinal elementswhich differ in length.

Still another object of the invention is an improved transfer coatingapparatus in which a continuous traveling film, having longitudinalelements which differ in length, is caused to contact generally evenlyacross its entire width with a coating transfer member.

A further object is the provision of a method and apparatus for applyinga layer of coating material onto a continuous traveling film, suchmethod and apparatus being simple, economical, flexible in use, andcapable of accurate control.

In the drawing, FIGURE 1 is a diagrammatic front view of the coatingapparatus of the present invention; and FIGURE 2 is a side viewillustrating the relationship of coating transfer and metering rollersemployed in the apparatus shown in FIGURE 1.

The above and other objects of the invention are achieved by a methodand apparatus in which a continuous advancing film, having longitudinaledge elements which are longer than other portions of the film is causedto make generally even or uniform contact along its entire width with atransfer or applicator roller from which a layer of coating material ofpredetermined and controlled thickness is transferred to the filmitself. The coating transfer roller has a peripheral surface which iscon- Car 3,4%,786 Patented Mar. 10, 1970 ice toured to compensate forthe differences in length between the edge and other elements of thefilm which is being coated so that such longer film edge elements travelgreater distances than the shorter of such elements. More particularly,in coating a film having floppy edges; that is, a film in which thelongitudinal edge portions are longer than the mid-portion thereof, thetransfer roller would have a double-tapered configuration as provided,for example, by a pair of truncated cones which are abutted andconnected together at their ends of smaller diameter. With a transferroller of this configuration, the longer edge portions of such filmwould engage with sections of the transfer roller which are of largerdiameter than the roller section which is contacted. by the mid-portionof the film. Thus, the longer edge portions of the film would travelgreater distances than the mid-portion of the film, with the net resultbeing a flattening of the film edges against the transfer rollersurface.

In conventional kiss coating apparatus, as well as in the apparatus ofthe present invention, the film being coated contacts with the surfaceof the transfer roller along an arc of from 5 to 15, during whichcontact the layer of coating material is transferred to the film. Thetransfer roller is positioned horizontally and the layer of coatingmaterial is deposited onto its surface by maintaining a pool of suchmaterial between the transfer roller surface and a co-operatingstationary dam or metering roller. Such dam or metering roller would beshaped to conform with the contoured shape of the transfer roller andwould be spaced therefrom a distance substantially equal to thethickness of the coating material which is desired.

A further and preferred arrangement for depositing a layer of coatingmaterial of controlled thickness onto the transfer roller involves theuse of a cylindrical metering roller which is adapted to be canted abouta point located in an axial plane of the metering roller which issubstantially perpendicular to an axial plane of the transfer roller.Such cylindrical metering roller is simple and less costly to fabricatethan a tapered dam or tapered metering roller, and is especially suitedfor use in coating of conventional films having longitudinal edgeportions which are longer than the remainder of the film.

More particularly, in the coating of a film having floppy edges, thecylindrical metering roller is positioned adjacent to but spaced fromthe transfer roller, which would be of double-tapered configuration, asdescribed above, so as to flatten, and more particularly, smooth thefilm in its transverse direction into a generally arcuate contour as itcontacts therewith. With the cylindrical metering roller disposedsubstantially parallel to the axis of the transfer roller, the layer ofcoating material deposited onto the transfer roller and subsequentlyapplied to the film would, of course, have a greater thickness at itscenter than at its edges. However, canting or inclining the meteringroller about its center and in a plane parallel to a similar planepassing through and including the axis of the transfer roller, theopening formed. by the opposing surfaces of the metering and transferrollers, while remaining the same at its center, is gradually increasedin width progressively from its center toward its ends. Actually, theopening which is formed by the transfer and metering rollers has oneside which extends generally helically along the transfer roller and onestraight side as defined by the surface of the metering roller. As aresult, the layer of coating material which issues from such opening is,in general, of uniform thickness even though the transfer roller whichassists in shaping such layer is contoured.

The degree to which the metering roller is canted will depend upon theparticular variations, if any, which may be desired in the coatingtransversely of the film length. More particularly, canting of themetering roller to a degree substantially equal to the slope of thetransfer roller tapered surface will dispose the surface of the meteringroller in parallel relationship to the opposite tapered portions of thetransfer roller so that a layer of coating material of generally uniformthickness across its entire width will be deposited upon the transferroller surface. On the other hand, canting the metering roller to agreater or lesser degree than the slope of the transfer roller surfacewill result in coating layers which are, respectively, thicker orthinner at their edges than at their mid-sections. Once the meteringroller has been canted to the desired degree it may, if necessary, bemoved horizontally toward or away from the transfer roller to vary thewidth of the opening between the rollers surfaces uniformly along itsentire length.

The slope of the transfer roller tapered surface will depend upon thedifferences in length of the logitudinal edge elements and the remainderof the particular film which is being processed. With conventionalregenerated cellulose films, a transfer roller in which the sectionswhich are to engage with the film edges are from about 5% to 70% greaterin diameter than at the mid-section of the roller will generally achievesatisfactory flattening of the film against the transfer roller surface.

In coating of regenerated cellulose film having floppy edges, thecontour of the transfer roller employed in the apparatus of the presentinvention will be symmetrical, as described above. This configuration,however, may be varied so as to accommodate the particular longitudinaledge variations in the film which is to be coated. For example, if thefilm is such as to have longitudinal edge portions which are longer thanthe remainder of the film and in themselves differ in length, thetransfer roller would, in effect, be formed of two sections of truncatedcones having surfaces which differ in taper or slope, with the smallestdiameter of the transfer roller being at such location as to receive thelongitudinal element of the film which is the shortest in length. Thecylindrical metering roller would be canted as heretofore described,with the exception that its inclination would occur about a point on itsaxis which is opposite the section of the transfer roller of smallestdiameter.

Referring now to the drawing, the apparatus of the present invention hasa suitable supporting framework, including spaced side plates 11 whichrotatably support the opposite ends of shafts 13 of coating transferrollers 15. Pairs of brackets 17 are fixed at 19 to the side plates 11and are each provided with a arcuate slot 21 which receives a pair ofpins 23 projecting from an adjacent metering roll support 25. Theoutermost ends of the pins 23 are threaded for receiving nuts 27 which,when tightened against the respective brackets 17, lock the supports 25in positions to which they have been adjusted.

The metering roll supports 25 are identical in construction, eachincluding bearing member 29 having a slot 31, for guiding a slide block33 as it is moved by an adjusting screw 35. The screws 35 are threadedthrough the hearing members 29 and are rotatably connected to therespective slide blocks 33 so as to move the latter linearly along theirguide slots.

A cylindrical metering roller 37 is mounted by a shaft 39 between a pairof slide blocks 33 and co-operates with an adjacent transfer roller indepositing a layer of coating material onto the transfer roller surfacefrom a pool 41 of such material, as supplied by a pipe 43. As inconventional apparatus, dams are provided to prevent the coatingmaterial from spilling over the ends of the rollers. The transfer andmetering rollers are all driven at the same speed by any suitable means,not shown, as for example by an endless belt driven by a single motorand laced over pulleys which are fixed to the ends of the respectiveroller shafts.

The film to be coated, indicated at 45, is drawn from its source ofsupply, not shown, guided by idler rollers 47 and 49 and then passed inbetween and in contact with 4 the coating transfer rollers 15. Thetransfer rollers 15 and the guide roller 49 are supported by the sideplates 11 in such positions as to cause the film 45 to contact each ofthe transfer rollers 15 along an arc of from 5 to 15 of its peripheralsurface. If necessary, additional guide rollers 49 may be provided toachieve this result.

In coating a conventional regenerated cellulosic film, such as film 45,having longitudinal edges which are longer than the middle portionthereof, the transfer rollers 15 would be of double-taperedconfiguration and, as heretofore described and shown in FIGURE 2, wouldcorrespond to a roller as formed by two turncated cones connectedtogether at their smaller ends. Normally a transfer roller which is from5 to 10% larger in diameter at its ends than at its center will achievea desired flattening or smoothing of a conventionally formed regeneratedcellulose film as it travels thereover. As heretofore described, and asalso shown in FIGURE 2, the metering rollers 37 are of cylindricalconfiguration.

In practicing the method of the present invention with the abovedescribed apparatus, the film 45 which is to be coated is first lacedover guide rollers 47 and 49, passed inbetween and in contact with thetransfer rollers 15 and then advanced to a suitable collection means,not shown. The metering rollers 37 are then adjusted relative to therespective transfer rollers 15 by movement of the screws 35 and theslide blocks 33 to which such screws are attached. With the supports 25free for movement, the respective metering rollers 37 are then cantedabout their centers in planes parallel to similar planes passing throughand including the axes of the transfer rollers. More specifically, eachmetering roller is tilted so that its axial is substantiallyperpendicular to an axial plane of the adjacent transfer roller, withthe point about which the metering roller is tilted lying along a lineat which such planes intersect. Once adjusted, the nuts 27 are tightenedto lock the supports in their adjusted positions.

With transfer rollers having a configuration as described above, themetering rollers are preferably canted to a degree equal to the slope ofthe transfer roller surface to provide the film with a coating ofgenerally uniform thickness across its entire width. As heretoforementioned, the metering rollers may be canted to a greater or lesserdegree than that indicated above if a coating which differs in thicknessacross its width is desired. Once adjusted as described above, themetering rollers may be moved horizontally toward or away from therespective transfer rollers if it is necessary to vary the openingbetween the roller surfaces along its entire length.

Flowable coating material is then delivered by the pipes 43 to provide apool 41 between each pair of metering and transfer rollers. Once set inoperation, the transfer rollers each carry, from the respective pools41, a layer of coating material which conforms in cross-section with theopening provided between the transfer roller and the adjacent meteringroller and apply the same to the film 45 while it is in contact with andflattened by such contoured transfer roller. After moving past thetransfer rollers, the film may be heated to dry the applied layers ofcoating material and is then collected.

I claim:

1. Apparatus for coating a continuous film having longitudinal edgeelements which are longer than the remainder of the film including aframe, a horizontally disposed coating transfer roller rotatably carriedby said frame, a metering roller, means supporting said metering rolleradjacent to said transfer roller with its longitudinal axis lying in aplane parallel to a similar plane passing through the axis of saidtransfer roller, means for supplying a pool of coating material inbetween said transfer and metering rollers, means for adjusting saidmetering roller relative to said transfer roller to provide an elongatedopening between the surfaces of said rollers, means for rotating saidtransfer and metering rollers at substantially the same speed and inopposite directions whereby a layer of coating material is carried onthe surface of said trans fer roller from the pool of coating materialand through said elongated opening, and means for advancing a film to becoated relative to and in contact with only a portion of the surface ofsaid transfer roller for applying a layer of coating material from saidtransfer roller to the film, said transfer roller having adouble-tapered configuration and being of largest diameter at its endsso as to cause the longer edge elements of the film to travel greaterdistances than the shorter elements thereof when the film is in contactwith said transfer roller.

2. Apparatus as defined in claim 1 wherein said metering roller is ofcylindrical construction and further including means for adjusting saidmetering roller into an inclined position in a plane substantiallyparallel to a plane passing through and including the axis of saidtransfer roller and about a point located along a line at which theplane of the metering roller intersects with a substantiallyperpendicular plane passing through and including the axis of saidtransfer roller.

3. Apparatus as defined in claim 2 wherein said transfer roller is ofsmallest diameter at its mid-section and wherein the point about whichthe metering roller is inclined is opposite the mid-section of thetransfer roller.

4. Apparatus as defined in claim 3 wherein the surface of the transferroller tapers substantially uniformly from the mid-section to the endsthereof and wherein the midsection of said transfer roller is from 5 tosmaller in diameter than the ends thereof.

5. A method of coating a continuous film having longitudinal edgeelements which are longer than the remainder of the film including thesteps of advancing the film in a longitudinal direction, smoothing thefilm in its transverse direction into a generally arcuate contour,contacting the generally arcuately contoured, advancing film evenlyacross its entire width with a shaped layer of flowable coating materialof uniform thickness, and solidifying the applied layer of coatingmaterial Z 6. A method as defined in claim 5 wherein the film isgenerally arcuately contoured in its tranverse direction by contactingfrom 5 to 15 of the peripheral surface of a rotatable transfer roller ofdouble-tapered configuration which is of largest diameter at its ends,and wherein said layer of coating material is applied onto the surfaceof the transfer roller at one location and is transferred to the film atanother location as the film engages therewith.

7. A method as defined in claim 6 wherein the thick ness of the layer offlowable coating material applied onto the transfer roller is controlledby a cylindrical metering roller which is disposed adjacent and cantedrelative to the transfer roller in a plane substantially parallel to anaxial plane of the transfer roller and about a point located along aline at which the plane of the metering roller intersects with asubstantially perpendicular plane passing through and including the axisof the transv fer roller.

References Cited UNITED STATES PATENTS l/1965 Parker 1l8252 6/1967 Thorp1l8262 X ALFRED L. LEAVITT, Primary Examiner CHARLES R. WILSON,Assistant Examiner US. 01. XR. 118246, 26;

mg UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 s9a7 D d March 10, 197

Inventor(s) Horace P, Fry JP It is certified that error appears in theabove-identified patent and that said Letters Patent are herebycorrected as shown below:

r- Column 1. line 32, "roating" should read rotating 7 Column 3 line 17,"lo itudinal" should read longitudinal line 22, 7073" should read 10%Column 1; line 12 "tuI'nc-ated" should read truncated line 32, after"axial" insert plane SIGNED KN SEALED JUL281970 N Attest:

'1 mum: E. sum. .1. Attestmg Officer Comissionn of PM.

